Good question, sorry I can't provide much help for an answer. I have owned two 5 series, a 530 xi 2001, and now this 535xi sportwagon 2010. I have NEVER had a flat in my life, and since I have roadside assistance, I don't worry about it too much. I would if I were you try not to deviate too much in tire size/tolerance in diameter. I have found that depending on where you are in the country, dealerships sell BMW's but don't know squat about them.